Motor vehicle disc brake systems generally utilize a disc brake rotor at each respective wheel. Each rotor, for example, generally includes two oppositely-facing annular friction surfaces which, during operation of the brakes, are engaged by two blocks of friction material (e.g., brake pads) that are moved towards one another into contact with the two friction surfaces so that frictional forces occur and slow the rotation of the rotor, and hence the wheel of the vehicle.
Under light braking pressures (i.e., used to control the speed of the vehicle), brake pads may make only partial contact with the rotor surfaces, leading to unstable frictional forces between the rotor and the brake pads. This unstable behavior of the rotor/pad friction pair may produce high dynamic contact forces, which can, for example, excite strong vibration of the brake pads. Since conventional brake rotors (which are generally formed of a gray cast iron) have multiple resonant frequencies in the audible frequency range, the vibration of the brake pads may in turn excite a resonant vibration in the brake rotor that produces an objectionable squeal noise during operation of the brakes.
In order to prevent squeal noise occurrence, brake components, such as, for example, brake pads and rotors, may be configured with dampers to reduce brake pad vibration and suppress rotor resonant vibration. Conventional damped pads and rotors may include, for example, dampers which utilize friction damping (i.e., Coulomb damping) from contact pressure between two surfaces that have whole-body motion relative to one another (i.e., full slip can develop between the surfaces). Such dampers may include, for example, solid inserts and damper rings, which create contact pressure between a surface of the insert/ring and a surface of the pad/rotor or a filler material within the pad/rotor.
Although such damped rotor/pad designs provide some vibration suppression, the damper effectiveness of such designs varies with brake temperature. The full slip condition between the sliding surfaces of such components changes with brake temperature, for example, which may result in a change in contact pressure between the surfaces and a resulting change in damper effectiveness (i.e., a decrease in damper effectiveness). Since the operating temperature range for a conventional brake component is very wide (e.g., from about −40° C. after an overnight in a cold climate during the winter to about 500° C. during an emergency stop from high speed or during a continuous use of the brakes while driving in a mountainous area), the friction damper effectiveness of such designs is also widely variable, and may not prevent squeal noise during certain temperature conditions.
It may, therefore, be advantageous to provide a brake component (e.g., a brake rotor and/or brake pad) with an improved damping capacity that continuously prevents brake squeal noise. It may also be advantageous to provide a brake component having an invariable damper effectiveness that is unaffected by brake temperature changes.